Patent GB-1258796-A (GB)
IPC: F16H47/08
Filed: 1969-08-01
Abstract: 1,258,796. Change-speed gear. FORD MOTOR CO. Ltd. 1 Aug., 1969, No. 35729/69. Heading F2D. In an automatic transmission on a motorvehicle, using ratio-establishing friction clutches 20, 78 and brakes 38, 64, applied by fluid pressure servos, a single servo 64 which is used for manual low forward, and reverse, has its individual pressure regulated by a 2-1 modulator valve 392 to a level suitable for smooth shifts into low, the modulator being disabled by reverse pressure 154, 390 supplied when reverse is selected at a manual valve 128, to raise the pressure level in that one servo. In both instances the established pressure level is subject, in common with the other servos, to control by the usual main pressure-regulator valve 86, which is loaded by throttle (TV) pressure 212, 122, as described below; has additional line pressure loading 154 for general augmentation of pressure in reverse; and speed responsive reduction by a cut-back valve 214. Gear arrangement.-The usual Simpson gear set, driven through a hydrodynamic torqueconverter, comprises two identical sun-ring- planet trains, with selective input to either the first ring or the common sun through clutches 30, 38; a one-way brake with lock up band brake 64 on the rear carrier for manual low and reverse; an intermediate brake 38 for the common sun; and the front carrier and rear ring connected together to output. The forward clutch 30 is effective for all three forward ratios; clutch 38 for direct-drive high and the single reverse.  Manual ranging control.-A manual selector valve 128 has settings R, N, D1, 2 and L. D1 provides for automatic shift between all three forward ratios, the first one-way, under control responsive to output speed and engine intake manifold depression. Settings 2 and L give fixed two way second and first ratios respectively, below a calibrated speed.  Control system, general.-1-2 and 2-3 shift valves 328, 280 are actuated by opposing governor and TV pressures 310, 194, the former provided by an output-driven two-stage centrifugal governor valve 312, 314, the latter by a primary throttle valve 180, regulated by a diaphragm unit 198 subject to engine intake manifold depression. The-valve 180 produces primary TV pressure 194 which, before acting on the shift valves, is processed to an increased value in a throttle booster valve 252 and then modulated to a suitable reduced level in a throttle modulator valve 270 (at the base of the 2-3 valve 280).  Fluid pressure supply and main regulation.-A single input-driven pump 80 supplies the system main 84, in which pressure is regulated by a main regulator valve 86, spilling first at 114 to the torque-converter, and later at 120 to exhaust. Regulator valve loading is by two springs, one, 102, reacting on a fixed abutment, the other, 104, on a pressure boost valve 106. Primary TV pressure 212, 122 acts constantly between differential lands 108, 110 of the boost valve 106, for TV responsive regulated output pressure 84.  Auxiliary loading of the regulator valve 86 is provided at the lower end of the pressure boost valve 106 through a line 124, fed with primary TV pressure 194 through a line 226 and a cutback valve 214, which, at higher speeds, is shifted down by governor pressure 310, to exhaust the line 226. Thus at low speeds and high TV pressure, e.g. on initial acceleration, higher servo pressure is provided. Depression of the cut-back valve 214 is delayed during initial acceleration until after 1-2 upshift, by an upward bias 374 on the cut-back valve, supplied by secondary TV pressure 266, 268 from the throttle booster valve 252, described below. The supply of TV pressure to the auxiliary load line 124 of the main pressure regulator 86 is under the further control of a line coasting boost valve 232, which provides increased servo pressure at closed throttle higher speeds, to sustain engine braking when entering manual second, when the line 226 would be exhausted by the governor-controlled cut-back valve 214. With TV pressure low, the line coasting boost valve 232 is in its upper position, shown, and at higher speeds the line 226 is exhausted through the cut-back valve 214 in its lower position, so that the auxiliary load line 124 is also exhausted. On entering manual 2 or L, in this condition, line pressure is received from the manual valve 128 through a line 174 or 166 respectively, which passes through a two-way non-return valve 362, line 244, line coast boost valve 232, and two-way non-return valve 230 to the auxiliary load line 124 for increasing loading of the main regulator 86.  At high TV pressure 212, the line coast boost valve 232 is depressed, blocking the branch 244 and allowing speed-responsive cut-back TV pressure 226 to pass directly to the auxiliary load line 124 through the two-way non-return valve 230.  In reverse the manual valve 128 feeds line pressure 84 through a line 154 to a space between differential lands 110, 112 of the pressure boost valve 106 for general pressure augmentation, In manual L the 2-1 modulator valve 392, forming the main subject-matter of this invention, is fed with line pressure from the manual valve 128 through a line 166, 1-2 shift-valve 328 (in downshift position shown) and line 348, which pressure is regulated by simple spring loading into the low brake line 348<SP>1</SP> by the 2-1 modulator valve. This softens 2-1 or D-L manual downshift. Reverse pressure 154, 390 from the manual valve shifts the 2-1 modulator 392 fully left, overcoming any modulating  action in reverse.  Shift valves.-The 1-2 and 2-3 shift valves 328, 280 are loaded downwards for upshift by governor pressure 310 and upwards by TV pressure, processed as follows. Primary TV pressure 194, 212 is first increased in a TV- loaded throttle booster valve 252, which uses primary TV pressure at 250 to regulate main pressure 84, 264 into a secondary TV line 266, 268. This passes to a throttle modulator valve 270 at the base of the 2-3 shift valve 280, where it is reduced by regulating action to modulated TV 278, which acts upwards on the lower end of the 2-3 shift valve 280, and between differential lands 342, 344 of a separate spool at the top of the 1-2 shift valve 328. The TV modulator valve 270 spills to an exhaust 274 which is closed by the manual valve 128 in 2 and L settings so that its modulating action is overruled.  Pressure to feed the respective clutches and brakes is fed directly to the 1-2 shift valve 328 through the forward clutch line 168, but it only reaches the 2-3 shift valve 280 at 308 through the upshifted 1-2 shift valve 328, so that even if the valve 280 upshifts, it remains ineffective until after upshift of the 1-2 valve 328. Manual 2 setting.-The manual valve 128 now feeds line pressure 84 through a line 174 to a space between the upper and lower spools of the 1-2 shift valve 328, thus upshifting it to second ratio. With the modulating action of the TV modulator valve 270 overruled by closure of its exhaust 274, the 2-3 shift valve 280 assumes downshift position below a predetermined governor speed. Manual L setting.-Feed to the line 348 of the reverse and low brake 64 is through the downshifted 1-2 shift valve 328 from a line 166, fed from the manual valve 128 in R and L only. If shift to manual L is made with the 1-2 valve upshifted, pressure 166 acts upwards on differential lands of the shift valve to oppose governor pressure 310 on deceleration and produce 2-1 downshift at a speed which is maintained constant regardless of the TV responsive variation in main pressure by a differentially landed downshift valve 350 which modulates line pressure supplied to it in L and R settings through the line 166, check-valve 362, and lines 360, 276, and feeds the modulated pressure through lines 274, 278 to the differential lands 342, 344 of the 1-2 shift-valve 328 for establishing the required downshift point.  Kickdown.-The downshift valve 350 is mechanically moved fully right at wide open engine-throttle to supply secondary TV pressure 368 direct to the line 274, downshifting both shift valves at calibrated speeds.  Shift timers (1), 2-3 back-out valve.-2-3 coasting or light throttle upshift is cushioned by a 2-3 back-out valve 370, which is loaded upwards by a spring and secondary TV pressure 266, and downwards by direct-drive clutch pressure 298 to provide TV controlled communication between line 298 and the apply line 324 of the second-ratio brake 38. This action is cut out in manual L by line pressure 276 acting beneath a manual low valve 376.  (2) Intermediate band accumulator valve.-For a 2-3 upshift the intermediate ratio brake 38 is released by applying pressure 302 to the release side of the brake servo, to overcome, with spring aid, the equal pressure on the apply side of the servo. During 3-2 downshift the brake 38 is re-applied by exhausting the release side of the servo. The rate of this exhaust, through a line 302, to an exhausting line 382, 2-3 shift valve 280, line 294 and manual valve 128, is controlled by an intermediate band accumulator valve 380, in which brake release pressure 302, acting on differential lands, opposes a spring and cutback TV pressure 229, 226, so that the exhaust rate is TV and speed responsive. Fig. 3, not shown, gives curves of servo pressure against engine intake pressure.